Protein gel electrophoresis is a ubiquitous technique in molecular biology research, pharmaceutical manufacturing, and other enterprises. The technique may be used to analyze the protein content of a biological sample or purify sufficient quantities of a protein of interest for later use. An essential aspect of protein gel electrophoresis is detection of sample proteins in the gel, which allows characterization of these proteins in terms of molecular weight, purity, amino acid content, etc. To aid such characterization, skilled practitioners often make use of a protein standard—a group of well-characterized proteins that is run in the gel alongside the sample proteins.
New technologies have made the detection of proteins following electrophoresis more sensitive, more specific, and less costly. Many of these technologies require that the proteins to be detected have particular features, such as specific amino acid motifs or covalently attached chemical groups.